AtlasPID: Fix for isTechnicolor, isHiddenValley, isExcited and isValid functions

• AtlasPID: Fix circular dependency in the definitions of isValid, isTechnicolor and isHiddenValley helper functions.
• AtlasPID: tighten definitions of isTechnicolor and isHiddenValley drop dependency on isValid. (NB These functions are currently unused in Athena, so if the definitions need to be revised further, this can be done in a follow-up MR.)
• AtlasPID: Improve robustness of definitions of isTechnicolor, isExcited and isHiddenValley
• AtlasPID: Re-order helper function calls within isBSM to better match how often models are used in ATLAS MC.
• AtlasPID: Further reordering and documentation for helper functions relating to PDG rule 11c.